To some degree, man has probably always desired to control conception, avoiding fertilization of the ovum without refraining from sexual intercourse if a baby is not wanted and achieving fertilization if a baby is wanted. Increasing concern in recent years about the prospect of overpopulation of the entire world has intensified the interest in family planning and conception control. On the other hand, many women desiring children are unable, without taking special measures, to achieve pregnancy. Thus, the control of conception involves both the achievement and the avoidance of conception, not on the basis of chance, but in accordance with the desires of the individuals involved.
Another aspect of conception control relates to the production of a boy or a girl baby. To varying degrees and in different ways, different cultures have followed practices thought to influence the sex of the baby to be conceived. Only in recent years, however, has this subject been given scientific treatment. It has been demonstrated that the probabilities of producing a baby of a desired sex may be enhanced by following certain procedures and practices.
An important consideration in both aspects of conception control is the timing of impregnation relative to the time of ovulation. Since the sperm is viable in the woman's reproductive organs for, perhaps, 4 or 5 days, and the ovum is viable for about 7 hours, it follows that intercourse more than 5 days before, or more than 7 hours after, ovulation cannot result in conception. This is the basic concept of the so-called rhythm method of birth control (which is only about 75 per cent effective due largely to the inability to predict the exact time of ovulation). The indispensability, then, of the coexistence of both the sperm and the ovum in the women's reproductive tract indicates the necessity of predetermining the time of ovulation which is the uncontrollable but controlling factor since the time of impregnation, whether by natural coitus or artificial impregnation, can, presumably, be controlled accordingly by the participants.
The sex of the conceived baby is the result of many factors and coincidences, only some of which are known. It has been observed that, in general, the semen contains both sperm carrying the male-producing Y chromosomes (androsperms) and sperm carrying the female-producing X chromosomes (gynosperms), the former usually initially predominating in number and mobile activity. While there is not yet full agreement among researchers of the effect of time of impregnation during the fertile period, and investigation is continuing, there appears to be full agreement that the time of natural impregnation or artificial insemination with respect to the time of ovulation affects the probabilities of having a boy baby or a girl baby, probably due to the effect of vaginal environmental factors on sperm viability. Thus, again, the predetermination of the time of ovulation is indispensable to the achievement of the desired result.
The ovulation cycle is controlled by four hormones, the most important of which is estrogen. This is a powerful hormone with several important functions in a woman's body. Flowing in the bloodstream, it performs a messenger service, signaling and triggering a complicated program of activity. Estrogen also stimulates the lining of the uterus, it acts on the vaginal mucosa and it stimulates secretion of an abundant translucent glair from the cervical glands necessary for the transport of sperm into the uterus.
The second hormone, follicle stimulating hormone (FSH), is dispatched from the pituitary. Liberation of this hormone appears to be controlled by the estrogen level from the previous cycle. FSH causes a single follicle in the ovary to grow. As the follicle matures it liberates estrogen in quantities which increase daily. This process is self-stimulating and causes a rapid build-up of estrogen in the blood during the period preceding ovulation.
The third hormone, lutenizing hormone (LH), is liberated from the pituitary gland when the estrogen content of the blood has reached a relatively high level. The LH surge induced by a rapid drop in estrogen level, contributes to a further swelling of the pre-ovulatory follicle.
The events leading to ovulation are completed when follicular rupture occurs with the liberation of an ovum. Thereafter, the estrogen content of the blood plasma continues to drop rapidly. The ruptured follicle turns into a body called the corpus luteum.
The corpus luteum now secretes estrogen as the follicle did, but it also secretes progesterone, the fourth hormone in the cycle. Progesterone stimulates more elaborate changes in the uterus to prepare it to receive a fertilized egg. The production of estrogen by the corpus luteum results in a second plateau of estrogen in the blood. Maturity of the corpus luteum is reached followed by its gradual regression with corresponding reduction in steroid secretion.
While the particular pattern of activity differs with different individuals, it repeats its characteristic form, cycle after cycle, in the body of a particular woman, absent disturbing influences. Charts can be, and have been, made showing consecutive daily levels of estrogen in the blood plasma and relating the resulting pattern with the time of ovulation. These charts show that the estrogen content of the blood peaks at least a day or two before ovulation, in some cases as much as 72 hours prior to ovulation. The estrogen level increases day by day until the peak level is reached, then rapidly decreases in advance of ovulation. Once the characteristic chart of a particular individual has been established by daily plasma tests over, perhaps, 3 or 4 months, it is possible thereafter to predict the time of ovulation well in advance of the occurrence. However, the determination of estrogen content in blood plasma requires laboratory procedure beyond the ability and facilities of a lay woman. For this reason it is not practical to employ estrogen level charts to predetermine ovulation time.
It is known that a woman's body temperature also varies in repeated patterns as the events of the ovulation cycle occur. Normally, the pre-ovulatory level of temperature is below average throughout that particular phase of the menstrual cycle and will rise or fall a small fraction of a degree over succeeding days. A sudden drop of a few tenths of a degree (F.) or more signals that ovulation is imminent and a succeeding sharp rise of a degree or so to a new plateau well above the average temperature of the full cycle indicates that ovulation has taken place. As a guide to the timing of impregnation, the temperature charts are not satisfactory because indications are both too late and not sufficiently certain.
The object and achievement of the present invention is to provide a method of predetermining the time of ovulation by means and procedures which are so simple that the ordinary woman can make her own determinations.
The method of this invention is based upon the discoveries that the vaginal fluid contains adenosine triphosphate (ATP) and that the concentration of ATP in the vaginal fluid varies from day to day throughout the ovulation cycle much as, in women, the estrogen level in blood plasma varies, especially during the critical ovum-forming period immediately preceding ovulation. The inventive concept involves the interval determination, as day by day, of ATP level in the vaginal fluid from which the time of ovulation can be predetermined as above described with reference to estrogen level but by simpler and less costly procedures. ATP levels are determined by measuring the intensity of light resulting from the reaction of the ATP content of successive, e.g. daily, samples of vaginal fluid with luciferase/luciferin in the presence of magnesium and manganese ions. The ease and accuracy of measurement of the light intensity by means of a simple meter is enhanced by buffering the solution to stabilize and prolong the life of the light emission.
For many reasons, artificial insemination is preferred to natural mating in both beef and dairy cattle but the cost is substantial and dependence upon observation of vaginal mucous discharge to signal estrous is unsatisfactory. The rapid development of the impregnation of cows (including heifers) by artificial insemination magnifies the importance of determining the time of ovulation by improved means to maximize the probability of effecting pregnancy.
At the present time, there are about 20,000,000 cows in the United States. In the year 1975, approximately 50 percent of the cows were artificially inseminated. The pregnancy rate resulting from natural mating at a single estrous in beef cattle averaged 70 percent while this average was 60 percent for artificial insemination. A principal reason for these low pregnancy rates is the failure to provide spermatozoa in the cows' reproductive tract at the time of ovulation; that is, impregnation at the wrong time.
In the bovine female, the ovulation cycle is controlled by hormonal interaction differing from that in women but similar for the purposes of the present invention in that the concentration of ATP in the vaginal fluid varies with the ovulation cycle so that the procedures herein described for determining the time of ovulation in women are directly applicable to determine the time of ovulation in cows. While the LH surge appears to respond to the level of estrogen in the blood in women, a similar release of LH appears to result from a precipitous decrease in the presence of progesterone in the blood plasma and milk in the case of cows. The rapid reduction in progesterone content signals LH release and estrous followed by ovulation. Thus, in the bovine female ovulation takes place while the estrogen titer is high whereas in women the estrogen content drops before the LH surge and continues to drop precipitiously just before ovulation takes place. The presence of ATP similarly varies measurably at the critical time prior to ovulation.
The general object of the invention, then, is to provide a practical means for predetermining with reasonable accuracy and a sufficient time in advance of the event the time of ovulation in women and in mammals having ovulation cycles, so that known procedures and principles, which depend for their effectiveness on such predetermination of the time of ovulation, may be employed to control the probabilities of conception and/or the sex of the conceived baby, in the case of women, and to insure pregnancy in animals. The technique of the invention may also serve as a diagnostic aid to the gynecologist in establishing management procedures to meet the needs of abnormal reproductive conditions in some women.
More specifically, an object of the invention is to provide a method for predetermining the time of ovulation in women by interval charting of the intensity levels of light chemically produced from the ATP content of samples of vaginal fluid taken at intervals over at least the ovum-forming period. The predetermination is made by comparison with previously prepared charts for the same individual showing the time of ovulation in relation to the chart form, this time having been determined by any of several indications, such as the Mittelschmerz pain, temperature shift method, etc.
Another object is to provide a practical method for predetermining the time of ovulation in cows to thus determine the best time for insemination for effecting pregnancy.
Further objects include the provision of techniques and means for simplifying and increasing the accuracy of light intensity determinations and thereby the accuracy of ATP level determinations.